U.S. patent application number 12/702045 was filed with the patent office on 2011-08-11 for magnetic read head.
This patent application is currently assigned to Seagate Technology LLC. Invention is credited to Yonghua Chen, Kaizhong Gao, Xilin Peng, Zhongyan Wang.
Application Number | 20110194213 12/702045 |
Document ID | / |
Family ID | 44353542 |
Filed Date | 2011-08-11 |
United States Patent
Application |
20110194213 |
Kind Code |
A1 |
Gao; Kaizhong ; et
al. |
August 11, 2011 |
MAGNETIC READ HEAD
Abstract
In some examples, a system comprising a data storage member
including a magnetic storage medium, the magnetic storage medium
having a plurality of magnetic bit domains aligned on at least one
data track, where a transition boundary between respective magnetic
bit domains defines a transition curvature. The system may further
comprise a magnetic read head including a first shield layer, a
second shield layer, and a read sensor stack provided proximate to
the first and second shield layers, where the magnetic read head
senses a magnetic field of each of the plurality of magnetic bit
domains according to a read playback sensitivity function. In some
examples, the shield layers and read sensor stack may be configured
to provide a reader playback sensitivity function that
substantially corresponds to the shape of the respective magnetic
bit domains.
Inventors: |
Gao; Kaizhong; (Eden
Prairie, MN) ; Peng; Xilin; (Walbridge, OH) ;
Wang; Zhongyan; (San Ramon, CA) ; Chen; Yonghua;
(Edina, MN) |
Assignee: |
Seagate Technology LLC
Scotts Valley
CA
|
Family ID: |
44353542 |
Appl. No.: |
12/702045 |
Filed: |
February 8, 2010 |
Current U.S.
Class: |
360/319 ;
G9B/5.104 |
Current CPC
Class: |
G11B 5/3912 20130101;
G11B 5/398 20130101; H01L 43/08 20130101 |
Class at
Publication: |
360/319 ;
G9B/5.104 |
International
Class: |
G11B 5/33 20060101
G11B005/33 |
Claims
1. The system of claim 21, further comprising, a data storage
member including a magnetic storage medium, the magnetic storage
medium having a plurality of magnetic bit domains aligned on at
least one data track, wherein a transition boundary between
respective magnetic bit domains defines a transition curvature,
wherein the magnetically responsive head comprises a first shield
layer, a second shield layer, and a read sensor stack provided
proximate to the first and second shield layers, wherein the
magnetic read head senses a magnetic field of each of the plurality
of magnetic bit domains according to a read playback sensitivity
function, wherein at least the shield layers and read sensor stack
are configured to provide the reader playback sensitivity function
that substantially corresponds to a shape of the respective
magnetic bit domains.
2. The system of claim 1, wherein the read playback sensitivity
function includes a first boundary, wherein the first boundary
substantially corresponds to the transition curvature defined by
the transition boundary.
3. The system of claim 2, wherein the read playback sensitivity
function comprises a first boundary that is concave with respect to
a transverse axis of the data track, the transverse axis
intersecting at least a portion of the read playback sensitivity
function.
4. (canceled)
5. The system of claim 1, wherein the magnetic storage medium is
magnetized by a perpendicular magnetic writing head.
6. The system of claim 1, wherein the read sensor stack is provided
substantially between the first and second shield layers.
7. The system of claim 1, wherein the read sensor stack comprises a
cap layer provided proximate to the first shield layer.
8. The system of claim 7, wherein the cap layer comprises a
magnetic portion and a non-magnetic portion.
9. The system of claim 8, wherein the magnetic portion comprises at
least one of nickel-iron or iron-cobalt alloys, wherein the
non-magnetic portion comprises at least one of carbon, aluminum
oxide, or silicon dioxide.
10. The system of claim 7, wherein the cap layer comprises a first
portion having a first magnetic permeability and a second portion
having a second magnetic permeability, wherein the first magnetic
permeability is greater than the second magnetic permeability.
11. The system of claim 7, wherein the cap layer is curved at a
boundary proximate to first shield layer.
12. (canceled)
13. The apparatus of claim 22, wherein the read field is
approximately symmetrical along a longitudinal axis of the data
track.
14. The apparatus of claim 22, wherein the read field comprises a
first boundary that is concave with respect to the second axis that
is substantially orthogonal to the alignment direction of a
plurality of bit domains, the second axis intersecting at least a
portion of the bit domains.
15. The apparatus of claim 22, wherein a track pitch ranges from
approximately 10 nanometers to approximately 150 nanometers.
16. (canceled)
17. The method of claim 23, wherein the predetermined asymmetric
read field comprises a curved boundary, wherein the curved boundary
substantially corresponds to the transition curvature.
18. The method of claim 23, wherein the means for producing a
predetermined asymmetric read field comprises a read sensor stack
provided substantially between a first shield layer and a second
shield layer, the read sensor stack comprising a cap layer
proximate to the first shield layer, wherein the cap layer is
curved at a boundary between the first shield layer such that a
distance between the first shield layer and second shield layer
varies along the boundary.
19. The method of claim 23, wherein the means for producing a
predetermined asymmetric read field comprises a read sensor
provided substantially between a first shield layer and a second
shield layer, the read sensor comprising a cap layer proximate to
the first shield layer, wherein the cap layer comprises a magnetic
portion and a nonmagnetic portion.
20. The method of claim 23, wherein the means for producing a
predetermined asymmetric read field comprises a read sensor
provided substantially between a first shield layer and a second
shield layer, wherein the read sensor is curved at a first boundary
between the first shield layer and curved at a second boundary
between the second shield layer.
21. A system comprising a magnetically responsive head with a read
field feature configured to produce a predetermined asymmetric read
field.
22. An apparatus comprising a magnetically responsive head with a
read field feature configured to produce a predetermined read field
symmetric about a first axis and asymmetric about a second axis,
the second axis being orthogonal to the first axis.
23. A method comprising providing a magnetically responsive head
with a read field feature and means for producing a predetermined
asymmetric read field with the read field feature.
Description
BACKGROUND
[0001] Magnetic data storage devices generally include magnetic
recording heads, which detect and modify the magnetic properties of
a magnetic storage medium to store data. For example, a recording
head may include a write head that "writes" data by magnetically
orienting discrete domains of a magnetic storage medium, generally
into one of two magnetic directions to represent a value of either
"0" or "1". In general, the respective magnetically oriented
domains are aligned on data tracks which divide the magnetic
storage medium. The recording head may further include a read head
that "reads" data by detecting the varying magnetic fields
emanating from the respective discrete domains on the magnetic
storage medium.
[0002] To increase the storage capacity of magnetic data storage
devices, the width of the respective data tracks, i.e., track
pitch, of magnetic storage mediums have been narrowed such that the
areal density of the magnetic storage medium has increased.
However, as the track pitch has narrowed, the degree of curvature
at the transition boundary between the magnetic domains i.e.,
transition curvature, which correspond to individual bits of data
written to each track to store data has increased. In some cases,
the resolution of the data playback process by a read head may be
reduced due to the presence and degree of transition curvature of
the bits written to a data track.
SUMMARY
[0003] The disclosure is directed to a system comprising a data
storage member including a magnetic storage medium, the magnetic
storage medium having a plurality of magnetic bit domains aligned
on at least one data track, wherein a transition boundary between
respective magnetic bit domains defines a transition curvature. The
system further comprises a magnetic read head comprising a first
shield layer; a second shield layer; and a read sensor stack
provided proximate to the first and second shield layers, wherein
the read head senses a magnetic field of each of the plurality of
magnetic bit domains according to a read playback sensitivity
function, wherein at least the shield layers and read sensor stack
are configured to provide a reader playback sensitivity function
that substantially corresponds to a shape of the respective
magnetic bit domains.
[0004] The details of one or more embodiments of the disclosure are
set forth in the accompanying drawings and the description below.
These and various other features and advantages will be apparent
from a reading of the following detailed description.
BRIEF DESCRIPTION OF DRAWINGS
[0005] FIG. 1 is a schematic diagram of an exemplary magnetic hard
disc drive including an example magnetic read/write head according
to one aspect of the disclosure.
[0006] FIGS. 2A and 2B are schematic diagrams illustrating portions
of two example data tracks.
[0007] FIG. 3 is a micro-magnetic simulation diagram illustrating
an example magnetic data track having curved transition
boundaries.
[0008] FIG. 4 is a plot illustrating an example read sensitivity
function of an example read head.
[0009] FIG. 5 is a plot illustrating an example read sensitivity
function of an example read head according to one embodiment of the
disclosure.
[0010] FIG. 6 is a schematic diagram illustrating an example read
head according to one embodiment of the disclosure.
[0011] FIGS. 7A-7F illustrate an exemplary technique that may be
utilized to fabricate the example read head of FIG. 6 according to
one embodiment of the disclosure.
[0012] FIG. 8 is a transmission electron microscopy (TEM)
micrograph of an exemplary read head substantially similar to the
exemplary read head shown in FIG. 6 using the exemplary technique
illustrated by FIGS. 7A-7F
[0013] FIG. 9 is a schematic diagram illustrating another example
read head according to one embodiment of the disclosure.
[0014] FIGS. 10A-10D illustrate an example technique for
fabricating an example shield layer with a curved surface.
[0015] FIG. 11 is a schematic diagram illustrating another example
read head according to one embodiment of the disclosure.
[0016] FIG. 12 is a transmission electron microscopy (TEM)
micrograph of an example read sensor.
DETAILED DESCRIPTION
[0017] In general, the disclosure is directed to systems, devices
and methods for sensing magnetic fields, e.g., as related to magnet
storage applications. For example, magnetic read heads configured
to provide tailored reader playback sensitivity functions are
described. A read head may detect a magnetic field emanating from a
magnetic storage medium according to the reader playback
sensitivity function associated with the read head. Such read heads
may be incorporated in the one or more magnetic recording heads
utilized in a hard disc drive. However, while embodiments of the
disclosure describe the sensing of magnetic fields with respect to
read heads used in hard disc drives, embodiments are not limited to
such applications, but instead may also be incorporated in other
suitable applications, such as those applications in which it is
desirable to precisely detect magnetic fields.
[0018] FIG. 1 illustrates an exemplary magnetic hard disc drive 100
including an example magnetic recording head 112 according to one
aspect of the disclosure. Disc drive 100 includes base 102 and top
cover 104, shown partially cut away. Base 102 combines with top
cover 104 to form the housing 106 of disc drive 100. Disc drive 100
also includes one or more magnetic storage members that include a
magnetic storage medium, which in FIG. 1 are one or more rotatable
magnetic data discs 108 that include a magnetic storage medium.
Data discs 108 are attached to spindle 114, which operates to
rotate discs 108 about a central axis. Magnetic recording head 112
is adjacent to data discs 108. Actuator arm 110 carries magnetic
recording head 112 for communication with each of the data discs
108.
[0019] Magnetic recording head 112 includes a write head (not
shown) that can write data to data discs 108 by generating magnetic
fields sufficient to magnetize discrete domains of the magnetic
storage medium of data discs 108. As used herein, each of these
discrete domains on the magnetic medium may be known as a magnetic
bit domain. The magnetic storage medium of data disc 108 is divided
into a plurality of concentric circular data tracks in which the
magnetic bit domains are aligned.
[0020] Magnetic recording head 112 also includes a read head (not
shown) that is capable of detecting the magnetic fields of the bit
domains of the magnetic storage medium. For example, a read head
may include a read sensor that senses the magnetic field of a bit
domain. As the magnetic field sensed by the read sensor changes, so
does the resistance of a current applied across the read sensor.
Based on the change in resistance, the read head is able to detect
the magnetic orientation of the bit domains of a magnetic storage
medium, which may correspond to either a value of "0" or "1". In
this manner, data discs 108 may store information as magnetically
oriented bits which may be written and read by recording head
112.
[0021] FIGS. 2A and 2B are schematic diagrams illustrating portions
of two exemplary data tracks. Specifically, FIG. 2A illustrates a
portion of data track 200 and FIG. 2B illustrates a portion of data
track 250. Data tracks 200 and 250 are examples of data tracks that
may divide a magnetic storage medium, such as, e.g., magnetic data
disc 108 of FIG. 1.
[0022] Referring to FIG. 2A, data track 200 is one of a plurality
of concentric circular data tracks that divide the magnetic storage
medium of a magnetic data disc. Accordingly, sides 202 and 204 of
data track 200 may be next to, or form the side of the other
similar data tracks dividing the magnetic storage medium. As
illustrated, a plurality of magnetic bit domains 210 including
individual magnetic bit domains 210A-210G are aligned on data track
200. Each of the plurality of magnetic bit domains spans the entire
width 212 of data track 200, which may be referred to as the track
pitch.
[0023] Further, each respective bit domain (210A-210G) exhibits a
magnetic field substantially in one of two magnetic orientations,
e.g., as a result of being magnetically oriented by a write head.
For example, magnetic bit domains 210C has a magnetic orientation
that is substantially opposite to the magnetic orientation of
magnetic bit domain 210D, as indicated by arrow tail 206 and arrow
head 208 (e.g., into and out of the plane of FIG. 2B).
[0024] Magnetic bit domain 210C and magnetic bit domain 210D are
separated by boundary 214. In accordance with the respective
magnetic orientations of bit domain 210C and 210D, boundary 214 may
be considered a transition boundary to the extent that boundary 214
represents a transition from one magnetic orientation to a
substantially opposite orientation as compared to boundary 220
which separates magnetic bit domains 210B and 210C that have like
magnetic orientations. Similarly, boundaries 218 and 216 are also
transition boundaries, as indicated by the respective magnetic
orientation indicators in FIG. 2A.
[0025] Referring to FIG. 2B, data track 250 is one of a plurality
of concentric circular data tracks that divide the magnetic storage
medium of a data disc, e.g., data disc 108 of FIG. 1. Accordingly,
sides 252 and 254 of data track 250 may be next to, or form the
side of the other similar data tracks dividing the magnetic storage
medium. As illustrated, a plurality of magnetic bit domains 260
including individual magnetic bit domains 260A-260G are aligned on
data track 250. Each of the plurality of magnetic bit domains spans
the entire width 262 of data track 250.
[0026] Similar to magnetic bit domains 210A-210G, each respective
bit domain 260A-260G in track 250 exhibits a magnetic field
substantially in one of two magnetic orientations, e.g., as a
result of being magnetically oriented by a write head. For example,
magnetic bit domains 260C has a magnetic orientation that is
substantially opposite to the magnetic orientation of magnetic bit
domain 260D, as indicated by arrow tail 256 and arrow head 258
(e.g., into and out of the plane of FIG. 2B).
[0027] Magnetic bit domain 260C and magnetic bit domain 260D are
separated by boundary 264. In accordance with the respective
magnetic orientations of bit domain 260C and 260D, boundary 264 may
be considered a transition boundary to the extent that boundary 264
represents a transition from one magnetic orientation a
substantially opposite orientation as compared to boundary 270
which separates magnetic bit domains 260B and 260C that have like
magnetic orientations. Similarly, boundaries 268 and 266 are also
transition boundaries, as indicated by the respective magnetic
orientation indicators in FIG. 2B.
[0028] Although FIGS. 2A and 2B illustrate transition boundaries
214, 216, 218, 264, 266 and 268 as distinct, smooth boundary lines
separating a bit domain of one magnetic orientation from another,
it is recognized that magnetic boundaries between magnetic bit
domains are not necessarily oriented as such. For example, in some
cases, magnetic bit domains may include a plurality of magnetic
grains in which substantially all of the magnetic grains have the
same magnetic orientation. Transition boundaries may be formed
along the boundaries of oppositely oriented grains according to the
shape of the boundary formed by individual grains. Accordingly, in
some examples, a transition boundary may not be a smooth line, but
instead a meandering boundary that is approximated by a smooth line
such as that shown in FIGS. 2A and 2B. As a result, boundaries 214,
216, 218, 264, 266 and 268 may only represent the general shape of
the magnetic transition between magnetic bit domains formed by
individual magnetic grains having substantially opposite magnetic
orientations aligned on a data track.
[0029] Notably, as illustrated by FIG. 2A, transition boundaries
214, 216, and 218 extend across the width 212 of data track 200 in
substantially a straight line. Conversely, as illustrated by FIG.
2B, transition boundaries 264, 266, and 268 do not extend
substantially straight across the width 262 of data track 250, but
instead form a curved transition boundary which spans the width 262
of data track 262. Such a curvature may be generally known as a
transition curvature.
[0030] As another example of curved transition boundaries, FIG. 3
is a micro-magnetic simulation diagram illustrating example
magnetic data track 300 having curved transition boundaries. Data
track 300 includes a plurality of magnetic bit domains 302 in which
the magnetic orientation of each respective magnetic bit domains
alternates sequentially between substantially opposite magnetic
fields. The magnetic fields associated with the plurality of
magnetic bit domains 302 are approximately indicated by the
relative color shown in FIG. 3, the darker areas indicating a
relatively strong magnetic field in one of two substantially
opposite magnetic orientations and the lighter areas separating the
individual magnetic bit domains corresponding to transition
boundaries.
[0031] Each transition boundary, e.g., transition boundary 306
separating magnetic bit domain 308 and magnetic bit domain 310,
extends across the width 304 of data track 300. Moreover, each
transition boundary is not a straight boundary but instead exhibits
a transition curvature. In this case, the transition boundary is
curved in the read direction 312 (which will be described in
further detail below with respect to data tracks 200 and 250) of
data track 300. As illustrated in the example of FIG. 3, the degree
of transition curvature of each of the respective transition
boundaries is substantially equal throughout the data track.
[0032] In this case, the plurality of magnetic bit domains 302
aligned on data track 300 may have been oriented by a perpendicular
write head. However, curved transition boundaries may be exhibited
by magnetic bit domains written by types of write heads other than
perpendicular write heads, e.g., write head capable of orienting
magnetic bit domains on a data track in bit densities that produce
curved transition boundaries. In some examples, write heads without
screw angle control will orient the magnetic domain such that
curved transition boundaries are exhibited, as precise control of
the screw angle may be very challenging.
[0033] In general, curved transition boundaries may be exhibited by
data tracks containing aligned magnetic bit domains. The presence
of curved transition boundaries and the degree of transition
curvature on a data track may result from a number of factors. In
some cases, curved transition boundaries between magnetic bit
domains may be related to the width of the data track on which the
magnetic bit domains are aligned. For example, with reference to
FIGS. 2A and 2B, the width 262 of track 250 is relatively less than
the width 212 of track 200. In some embodiments, width 262 of track
260 may range from approximately 10 nanometers to approximately 150
nanometers, such as approximately 10 nanometers to approximately
100 nanometers, or approximately 30 to approximately 60 nanometers,
or approximately 75 nanometers to approximately 150 nanometers.
[0034] Further, the degree of transition curvature may be related
to the width of a data track. In some cases, the degree of
curvature of a curved transition boundary may increase as the
relative width of a data track decreases. For example, the curved
transition boundaries between magnetic bit domains on a data track
may exhibit a greater degree of curvature compared to the degree of
curvature exhibited by curved transition boundaries on a data track
with a relatively greater track width.
[0035] In some examples, the degree of transition curvature
exhibited by transition boundaries between magnetic bit domains by
may be expressed with respect to a comparison of lengths 274 and
276, shown in FIG. 2B. As shown, length 274 approximately
corresponds to the greatest distance with respect to any point
along the transition boundary in the read direction, e.g., the
nexus of curved transition boundary 266, furthest from the
approximate point in the read direction in which boundary 266 meets
track side 254. Length 276 approximately corresponds to the total
length of an individual bit domain measure, e.g., the approximate
length of magnetic bit domain 210F in the read direction.
[0036] The transition curvature exhibited by magnetic bit domains
on a data track included on a magnetic storage medium may vary in
embodiments of the disclosure. For example, with reference to
lengths 274 and 276 on data track 250 of FIG. 2B, length 274 with
respect to length 276 in an embodiment of the disclosure may be
greater than, equal to, or less than other embodiments of the
disclosure. In some examples, length 274 may range from
approximately 5 percent to approximately 300 percent of length 276,
such as approximately 20 percent to approximately 300 percent of
length 276, or approximately 30 percent to approximately 50 percent
of length 276.
[0037] As previously described, a magnetic read/write head
typically includes a read head that detects the magnetic fields of
the respective bit domains on a magnetic storage medium. For
example, with reference to FIGS. 2A and 2B, the magnetic fields
emanating from the plurality of magnetic bit domains 210 and 260
aligned in data tracks 200 and 250, respectively, may be detected
by a read head located proximate to the air bearing surface of the
data discs which contain the respective data tracks. Data tracks
200 and 250 may be moved relative to a read head in substantially
the read direction indicated by arrows 222 and 272, respectively,
e.g., by rotating data disc 108 attached to spindle 114 about a
central axis relative to recording head 112, as illustrated in FIG.
1. As described previously, a read head may include a read sensor
that senses the magnetic field of a bit domain, e.g., plurality of
magnetic bit domains 210 and 260 on data track 200 and 250,
respectively, when the read sensor is properly aligned with respect
to data tracks 200 and 250. By moving data track 200 or 250
relative to a read head and, therefore, the read sensor of the read
head, read sensor senses changes in the magnetic field that result
from a differences in the magnetic orientation of the plurality of
magnetic bit domains 210 or 260, respectively. For example, a read
sensor may sense a change in magnetic field as data track 200 is
moved relative to the read head such that the magnetic field sensed
by the read sensor changes from the magnetic field of bit domain
210C to the magnetic field of bit domain 210D.
[0038] In general, a read head senses magnetic fields according to
a read playback sensitivity function associated with the read head.
For example, a read playback sensitivity function may represent the
relative sensitivity of a read sensor to magnetic fields emanating
from a magnetic storage medium with respect to the position
relative the read sensor. In some cases, a read head may sense
magnetic fields emanating from a magnetic storage medium according
to a read playback sensitivity function that is approximately
symmetrical with respect to both a longitudinal axis of the data
track, and the track pitch direction, i.e., transverse direction,
when aligned with a data track.
[0039] FIG. 4 is a plot illustrating an example read playback
sensitivity function. The exemplary read playback sensitivity
function illustrated by plot 400 is substantially symmetrical along
a first axis 402 and a second axis 404. In general, the relative
degree of sensitivity of a read head which senses magnetic fields
according to the read sensitivity function of FIG. 4 is represented
in plot 400 based to the relative color of the plot. As indicated
by plot 400, the relative sensitivity of the read head which senses
magnetic fields according to the read playback sensitivity function
of plot 400 is greatest at approximately the center 406 of the read
sensitivity function, which in the case is approximately
intersection of first axis 402 and second axis 404. Furthermore, as
shown, the sensitivity of the read head decreases at varying rates
moving away from center 406 of the read playback sensitivity
function according to relative color illustrated in plot 400.
[0040] A read playback sensitivity function consistent with plot
400 may be suitable to sense the magnetic fields emanating from
magnetic bit domains, e.g., such as magnetic bit domains that are
also approximately symmetrical with respect to both the read
direction and track width direction. For example, a read head which
senses magnetic fields according to the read playback sensitivity
function illustrated by plot 400 may be positioned to sense the
magnetic fields of the plurality of magnetic bit domains 210 on
track 200 of FIG. 2A. In some cases, a read head that senses
magnetic fields according to the read playback sensitivity function
illustrated by plot 400 may be positioned such that center 406 of
the read playback sensitivity function is approximately centered on
width 212 of data track 200, and oriented such that direction 408
is consistent with read direction 222. As such, first axis 402 may
be a longitudinal axis and second axis 404 may be a transverse axis
with respect to data track 200.
[0041] However, a read head which senses magnetic fields according
to a read playback sensitivity function such as that illustrated by
plot 400 may not always be desirable. In some cases, magnetic bit
domains are not necessarily substantially symmetrical with respect
to both read direction and track width direction. For example, as
illustrated by FIG. 2B, curved transition boundary 264 influence
magnetic bit domains 210B and 210C such that the shape of the
respective bit domains are not symmetrical along a transverse axis
of track 250.
[0042] Consequently, a read head which senses magnetic fields
according a read playback sensitivity function that is inconsistent
with the shape of magnetic bit domains aligned on a data track
and/or the shape of the transition boundaries between respective
bit domains may not possess a sufficient reader resolution to
adequately read data stored on a data track containing the magnetic
bit domains. In some examples, the signal to noise ratio in such
cases may prevent a read head from adequately sensing transitions
between magnetic bit domains, preventing read head from accurately
reading data stored on the magnetic data track. For example, a read
head that senses magnetic fields according to a read playback
sensitivity function inconsistent with curved transition boundaries
may sense an undesirable amount of the magnetic field of one or
more magnetic bit domains proximate to an individual magnetic bit
domain. As a result, the overall change in resistance of a current
applied across the read sensor in the read head may not be adequate
to detect the magnetic orientation, or transition thereof, of the
respective magnetic bit domains on a data track, leading to an
increase in bit error rate.
[0043] In accordance with aspects of the disclosure, a read head
may be provided which senses magnetic fields according to a read
playback sensitivity function that more suitably corresponds to
magnetic bit domains having at least one curved transition
boundaries.
[0044] As previously described, in one aspect, the disclosure
relates to a system comprising a data storage member including a
magnetic storage medium, the magnetic storage medium having a
plurality of magnetic bit domains aligned on at least one data
track, wherein a transition boundary between respective magnetic
bit domains defines a transition curvature. The system further
comprising a magnetic read head comprising a first shield layer; a
second shield layer; and a read sensor provided proximate to the
first and second shield layers, wherein the read head senses a
magnetic field of each of the plurality of magnetic bit domains
according to a read playback sensitivity function, wherein at least
the shield layers and read sensor stack are configured to provide a
reader playback sensitivity function that substantially corresponds
to a shape of the respective magnetic bit domains.
[0045] In another aspect, the disclosure relates to a system
comprising a data storage member including a magnetic storage
medium, the magnetic storage medium having a plurality of magnetic
bit domains aligned on at least a data track. The system further
comprising a magnetic read head comprising a first shield layer; a
second shield layer; and a read sensor provided substantially
between the first and second shield layers, wherein the shield
layers and read sensor are configured to provide a reader playback
sensitivity function, wherein the read head senses a magnetic field
of the respective magnetic bit domains contained on the magnetic
storage medium according to the reader playback sensitivity
function, wherein the reader playback sensitivity function is
approximately asymmetrical along a transverse axis of the data
track.
[0046] In still another aspect, the disclosure relates to a system
comprising a data storage member including a magnetic storage
medium, the magnetic storage medium having a plurality of magnetic
bit domains aligned on at least a data track, wherein a transition
boundary between respective magnetic bit domains defines a
transition curvature. The system further comprising a read head
comprising means for creating a reader playback sensitivity
function associated with the magnetic read head, wherein the reader
playback sensitivity function substantially corresponds to a shape
of the respective magnetic bit domains.
[0047] FIG. 5 is a plot illustrating an example read playback
sensitivity function according to the disclosure. In accordance
with some embodiments of the disclosure, the read sensitivity
function illustrated by plot 500 corresponds to a magnetic bit
domain that has at least one curved transition boundary. As shown,
the read playback sensitivity function illustrated by plot 500 is
substantially symmetrical with respect to first axis 502. Contrary
to the read playback sensitivity function illustrated by plot 400
of FIG. 4, the read playback sensitivity function illustrated by
plot 500 is substantially asymmetrical with respect to second axis
504.
[0048] As indicated by plot 500, the relative sensitivity of the
read head which senses magnetic fields according to the read
playback sensitivity function of plot 500 is greatest at
approximately point 506 of the read sensitivity function and
decreases at varying rates moving away from point 506 towards the
outer boundaries of plot 500. Contrary to the read playback
sensitivity function represented by plot 400, portion 510 of the
outer boundary of plot 500 is substantially concave with respect to
second axis 505. In some embodiments, such a curved boundary
portion may substantially correspond to the transition curvature of
a magnetic bit domain.
[0049] A read playback sensitivity function consistent with plot
500 may be suitable to sense the magnetic fields emanating from
magnetic bit domains having one or more curved transition
boundaries. In general, a read head may be configured to provide
for read playback sensitivity function that substantially
corresponds to the shape of magnetic bit domains having one or more
curved transition boundaries. For example, a read head which senses
magnetic fields according to a read playback sensitivity function
consistent with plot 500 may be provided to sense the magnetic
fields emanating from plurality of magnetic bit domains 260 aligned
on data track 250 of FIG. 2B. In some embodiments, such a read head
may be positioned such that center 506 of the read playback
sensitivity function is approximately centered on width 262 of data
track 250, and oriented such that direction 508 is consistent with
read direction 272. When oriented as such, first axis 502 may be a
longitudinal axis and second axis 504 may be a traverse axis with
respect to data track 250.
[0050] FIG. 6 is a schematic diagram illustrating an example read
head according to one embodiment of the disclosure. Read head 600
includes first shield layer 602, second shield layer 604, read
sensor stack 606 proximate to shield layers 602, 604, insulator
layers 222A, 222B and permanent magnet (PM) layers 220A, 220B. As
shown, read sensor stack 606 is provided substantially between
first shield layer 602 and second shield layer 604. Insulator
layers 622A, 622B is provided between read sensor stack 606 and PM
layers 220A, 220B, respectively. Insulator layers 622A, 622B are
also provided between second shield layer 604 and PM layers 620A,
620B, respectively.
[0051] As will be described, read head 600 may be utilized in a
magnetic read/write head to read data contained on a magnetic
storage medium in which the transition boundaries between magnetic
bit domains define a transition curvature, such as, e.g., magnetic
data track 250 of FIG. 2B. Data track 250 is included in FIG. 6 to
conceptually illustrate the position of read head 600 relative to
data track 250. Read head 600 may fly over the surface of data
track 250 to read the data stored on magnetic storage medium by
detecting the magnetic fields of the respective magnetic bit
domains aligned on data track 250. For example, as configured in
FIG. 6, magnetic read head 600 may provide means for creating a
reader playback sensitivity function associated with the magnetic
read head 600, where the reader playback sensitivity function
substantially corresponding to a shape of the respective magnetic
bit domains aligned on the data tracks of a magnetic storage
medium. In some embodiments, the read playback sensitivity function
may be similar to that represented by plot 500 of FIG. 5.
[0052] In general, the read playback sensitivity function that read
head 600 senses magnetic fields from data track 250 according to
may be influenced by the position of first and second shield layers
602, 604. In the embodiment illustrated in FIG. 6, first and second
shield layers 602, 604 reduce or substantially block extraneous
magnetic fields, such as, for example, those from adjacent magnetic
bit domains on data track 250 from impacting read sensor stack
606.
[0053] Insulating layers 622A and 622B may include aluminum oxide
and/or any other suitable material. PM layers 620A and 620B may
include nickel-iron (NiFe) alloys, e.g., permalloy, and/or any
other suitable material. Furthermore, as shown, read sensor stack
206 includes a plurality of individual layers 610-615, although the
exact number of layer and the function of each layer may vary in
embodiments of the disclosure. In this example, for example, layers
610 and 611 may be reference layers, layers 613 and 614 may be free
layers.
[0054] Notably, read sensor stack 606 also includes cap layer 615
proximate to first shield layer 602. Cap layer 615 includes
non-magnetic portion 616 located between magnetic portions 618A and
618B. In general, non-magnetic portion 616 may include a material
which has a relatively low magnetic permeability. For example,
suitable materials for non-magnetic portion 616 may include carbon
or aluminum oxide, and combinations thereof, or any other suitable
oxide, such as, e.g., oxides of silicon, such as silicon dioxide,
nitrides and/or carbides. In contrast, magnetic portions 618A, 618B
may include a material which has a relatively high magnetic
permeability. For example, suitable materials for magnetic portions
618A, 618B may include nickel-iron (NiFe) alloys, e.g., permalloy,
and/or iron-cobalt. Accordingly, in some embodiments, the magnetic
permeability of magnetic portions 618A, 618B is greater than the
magnetic permeability of non-magnetic portion 616.
[0055] The location of magnetic portions 618A, 618B in cap layer
615 substantially corresponds to the edges of data track 250 such
that the respective portions influence the sensitivity of read head
600 at approximately the edges of data track 250. Further, the
location of non-magnetic portion 616 in cap layer 615 substantially
corresponds to the center portion of data track 250 such that
non-magnetic portion 616 influences the sensitivity of read head
600 at approximately the center portion of data track 250. Due in
part to the relatively high magnetic permeability of portions 618A,
618B of cap layer 615 corresponding to the edges of data track 250
and low magnetic permeability of portion 616 of cap layer 615
corresponding to the center portion of data track 250, the
effective gap length sensitivity of read head 600 may be reduced.
In this manner, cap layer 615, in combination with at least shield
layers 602, 604 influences the read playback sensitivity function
associated with read head 600.
[0056] Overall, as configured in FIG. 6, the read playback
sensitivity function associated with read head 600 may
substantially correspond to the shape the respective magnetic bit
domains aligned on date track 250. For example, read head may sense
magnetic fields according to a read playback sensitivity function
such as the represented by plot 500 illustrated in FIG. 5. In some
embodiments, cap layer 615 may provide for a read playback
sensitivity function which has at least one boundary that
corresponds to the curved transition boundary of the magnetic bit
domains aligned on data track 250.
[0057] Read head 600 may be fabricated using any suitable technique
that allows for a configuration substantially as shown in FIG. 6.
For example, FIGS. 7A-7F illustrate an exemplary technique that may
be utilized to fabricate read head 600 of FIG. 6.
[0058] Referring to FIG. 7A, a plurality of materials are deposited
on a surface of shield layer 704 to form plurality of layers 706
which correspond to individual layers 610-614 and non-magnetic
portion 616 of layer 615 that form read sensor stack 606 of FIG. 6.
Shield layer 704 corresponds to second shield layer 604 of read
head 600 of FIG. Individual layers may be deposited as shown in
FIG. 7, e.g., by any suitable technique known in the art.
[0059] In some embodiments, layer 716 includes carbon and may
function as a CMP stop layer. Thickness 710 of layer 716 may vary
depending on a number of factors, including the properties desired
for the read head resulting from the fabrication process. For
example, in some cases, thickness 710 of layer 716 may range from
approximately 1 nanometer to approximately 50 nanometers, such as
approximately 5 nanometers to approximately 10 nanometers.
[0060] Resist layer 708 is located between photoresist layer 702
and surface 712 of layer 716. As illustrated by FIG. 7A, width 730
of resist layer 708 is less than width 728 of photoresist layer
702, such that resist layer 702 is an undercut layer with respect
to photoresist layer 702. Such a configuration may be accomplished
utilizing any suitable technique. For example, surface 712 of layer
716 may coated with high solubility polydimethylglutarimide (PMGI),
and the surface of the PMGI coating may subsequently be coated with
photoresist. In some cases, the PMGI and/or photoresist coating may
be applied using a spin coating procedure. The photoresist may then
be exposed according to the desired width 728 of layer 702, and
then developed along with the PMGI to form photoresist layer 702
and resist layer 708, including PMGI in this case, having an
undercut configuration as shown in FIG. 7A.
[0061] Referring to FIG. 7B, argon ion milling may be used to
remove a portion of the plurality of layers 705 such that the
remaining portion of layers 705 has a width 724 corresponding to
the width desired for the read sensor stack of the read head formed
from the fabrication process. Redeposition layers 718A and 718B
form as a result of the redeposition of a portion of the layer
material being removed by the ion milling process. As shown in FIG.
7B, redeposition layers 718A, 718B occupy the undercut area formed
by resist layer 708 and photoresist layer 702. Width 734 represents
the recess of layer 716 from edge of remaining layers of reader
stack 706. Although not limited to such dimensions, in some
examples, length 724 may be approximately 50 nanometers to
approximately 100 nanometers, and length 734 may range from
approximately 5 nanometers to approximately 15 nanometers.
[0062] Referring to FIG. 7C, insulator material is deposited to
form insulator layers 722A and 722B, and PM material is
subsequently deposited to form PM layers 720A and 720B as shown in
FIG. 7C.
[0063] Referring to FIG. 7D, photoresist layer 702 and resist layer
708 are removed, e.g., using a plasma ashing and/or lift-off
process.
[0064] Referring to FIG. 7E, a touch-up CMP process is used to
remove portions of PM layers 720A, 720B and redeposition layers
720A, 720B.
[0065] Referring to FIG. 7F, shield material is deposited on
exposed surface 732 to form shield layer 702 which corresponds to
first shield layer 602 of FIG. 6. The resulting read head 700 has
substantially the configuration as read head 600 of FIG. 6.
Accordingly, the exemplary technique illustrated by FIG. 7A-7F may
be used to fabricate read head 600 of FIG. 6.
[0066] FIG. 8 is a transmission electron microscopy (TEM)
micrograph of an exemplary read head 800 substantially similar to
read head 600 shown in FIG. 6 using the exemplary technique
illustrated by FIGS. 7A-7F. The micrograph in FIG. 8 illustrates
read head 800 including first shield layer 802, second shield layer
804, and read sensor stack 806 having cap layer 815. Cap layer 815
includes non-magnetic portion 816 and magnetic portions 818A and
818B. As configured, read head 800 may sense magnetic fields
according to a read playback sensitivity function that
substantially corresponds to the shape of a magnetic bit domains
having curved transition boundaries, e.g., such as the read
sensitivity function illustrated by plot 500 in FIG. 5.
[0067] In some embodiments, the structure and/or composition of a
read sensor stack of a read head may be provided such that the read
sensitivity playback function associated with the read head
corresponds to the shape of magnetic bit domains having at least on
curved transition boundary. For example, read sensor stack 606 of
read head 600 in FIG. 6 includes cap layer 615 which has magnetic
portions 618A, 618B and non-magnetic portion 616 as described
previously. However, in some embodiments, the shield geometry of a
read head proximate to a read sensor stack may be provided such
that the read sensitivity playback function corresponds to the
shape of magnetic bit domains having at least on curved transition
boundary. Such a configuration may be in addition to, or in
alternative to, providing composition and/or structure of one or
more layers of a read sensor stack of a read head to allow for a
read sensitivity playback function as described.
[0068] FIG. 9 is a schematic diagram illustrating another example
read head according to one embodiment of the disclosure. As shown,
read head 900 includes first shield layer 902, second shield layer
904, read sensor stack 906, insulator layers 922A, 922B and PM
layers 920A, 920B. Insulator layers 922A, 922B and PM layers 920A,
920B are substantially similar to those layers described with
respect to read head 600 of FIG. 6.
[0069] As illustrated by FIG. 9, the shield geometry of read head
900 proximate to read sensor stack 906 with respect to first shield
layer 902 and second shield layer 904 is different that of the
configuration of read head 600 in FIG. 6. For instance, second
shield layer 904 includes portion 932 forms a curved boundary 934
between read sensor stack 906 and second shield layer 904. As
configured, second shield layer 904 may be described as having a
curved surface, which may be fabricated using a suitable
fabrication process, e.g., by using a process such as that
described with respect to FIG. 10.
[0070] Read sensor stack 906 includes layers 910-914 which are
substantially the same as described with respect to layers 610-614
of read sensor stack 606 of FIG. 6. However, as illustrated by FIG.
9, the structure of read sensor stack 906 differs from that of read
sensor stack 606. Particularly, each of the individual layers
910-914 exhibits a curvature consistent with that of curved
boundary 934 between read sensor stack 906 and second shield layer
904. The overall structure of read sensor stack 906 exhibits a
substantially similar curvature. As a result, the read sensor stack
906 provides for a curved boundary 936 between read sensor stack
906 and first shield layer 902.
[0071] Similar to read head 600, read head 900 may be utilized in a
magnetic read/write head to read data contained on a magnetic
storage medium in which the transition boundaries between magnetic
bit domains define a transition curvature, such as, e.g., magnetic
data track 250 of FIG. 2B. Read head 900 may fly over the surface
of data track 250 to read the data stored on magnetic storage
medium by detecting the magnetic fields of the respective magnetic
bit domains aligned on data track 250. For example, magnetic read
head 900 may provide means for creating a reader playback
sensitivity function associated with the magnetic read head 900,
where the reader playback sensitivity function substantially
corresponding to a shape of the respective magnetic bit domains
aligned on the data tracks of a magnetic storage medium. In some
embodiments, the read playback sensitivity function may be similar
to that represented by plot 500 of FIG. 5.
[0072] Although curved boundary 934 of FIG. 9 is shown as a smooth,
arcuate boundary it is recognized that a configuration which do not
possess such a geometry may also allow for read head 900 to read
data contained on a magnetic storage medium in which the transition
boundaries between magnetic bit domains define a transition
curvature, e.g., by allowing for a read playback sensitivity
function similar to that of FIG. 5. In some embodiments, portion
932 of shield layer 904 may protrude in a manner such that all or
portions boundary 934 are not arcuate but still may effectively
allow read head 900 to adequately detect magnetic bit domains
and/or transitions exhibiting curved transition profiles, e.g.,
according to a reader playback sensitivity function similar that of
FIG. 5.
[0073] FIGS. 10A-10D illustrate an example technique for
fabricating an example shield layer with a curved surface, such as
shield layer 904 of FIG. 9. As shown in FIG. 10A, a photoresist,
such as, a thin photoresist, e.g., 100 nm, may be deposited on
shield layer 1004 such that a portion of the surface of shield
layer 1004 is covered by photoresist layer 1002. In general, the
portion of the surface of shield layer 1004 covered by photoresist
layer 1002 roughly corresponds to the area of shield 1004 that will
include a curved surface. In some embodiments, photoresist layer
1002 may be deposited such that one or more aspects of the desired
curved surface, including, e.g., the geometry of the curved surface
of shield layer, may be controlled.
[0074] Referring to FIG. 10B, photoresist layer 1002 is baked such
that the material of layer 1002 is allowed to flow as desired. At
the appropriate time, a dilute oxygen plasma trimming process may
be applied to shape the photoresist layer 1002, e.g., similar to
that shown in FIG. 10B.
[0075] Referring to FIG. 10C, reactive ion beam milling with oxygen
plasma trimming may be utilized to gradually remove at least a
portion of photoresist layer 1002, in addition to portions of
shield layer 1004, as indicated by FIG. 10C.
[0076] Referring to FIG. 10D, any remaining portion of photoresist
layer 1002 may be removed to leave shield layer 1004 with a curved
surface. As shown in FIG. 10D, shape of shield layer 1004 is
substantially similar to that of shield layer 904 of FIG. 9. When
shield layer 1004 in configured as shown in FIG. 10D, shield layer
1004 may be utilized to fabricate a read head with a curved read
sensor stack, such as read head 900 of FIG. 9. For example, read
sensor layers may be deposited onto to surface of shield layer,
resulting in a curved reader sensor stack corresponding to the
curved surface of shield layer 1004.
[0077] While the example technique of FIGS. 10A-D may be utilized
to fabricate a shield layer with a curved surface as described,
fabrication of such a shield layer is not limited to such a
technique. Rather, any suitable technique for fabricating a shield
layer with the same or similar configuration to that of shield
layers 904 and/or 1004 may be utilized.
[0078] Furthermore, while the curved surface of a shield layer is
described as resulting in a curved reader stack, it is recognized
that a similar configuration may be achieved by depositing reader
stack layers on a shield layer with an indention in the surface
rather than a protrusion, such as exhibited by first shield layer
902 of FIG. 9.
[0079] FIG. 11 is a schematic diagram illustrating another example
read head 1100 according to one embodiment of the disclosure. As
shown, read head 1100 includes first shield layer 1102, second
shield layer 1104, read sensor stack 1106, insulator layers 1122A,
1122B and PM layers 1120A, 1120B. Insulator layers 1122A, 1122B and
PM layers 1120A, 1120B are substantially similar to those layers
described with respect to read heads 600 and 900 of FIGS. 6 and 9,
respectively.
[0080] As illustrated by FIG. 11, read sensor stack 1106 is
provided substantially between shield layers 1102 and 1104. Read
sensor stack 1106 includes individual layers 1110-1114 which are
substantially the same as described with respect to layers 610-614
of read head 600 of FIG. 6. Further, read sensor stack 1106
includes cap layer 1115 proximate to first shield layer 1102. Cap
layer 1115 may include any suitable material that allows for a read
sensitivity function as described herein. In some examples, cap
layer materials may include materials that are substantially
nonmagnetic but electrically conductive. For example, cap layer
1115 may include one or more of ruthenium (Ru), chromium (Cr), gold
(Au), silver (Ag), and the like.
[0081] In general, cap layer 1115 exhibits a curvature along
boundary 1135 with first shield layer. As a result, boundary 1135
between cap layer 1115 and first shield layer 1102 exhibits a
curvature consistent with the shape of cap layer 1115, unlike
boundary 1134 between read sensor stack 1106, which does not
exhibit a curvature. Accordingly, the shield geometry is such that
the distance between boundary 1135 of first shield layer 1102 and
boundary 1134 of second shield layer 1104 varies proximate to read
sensor stack 1106. For example, as indicated by FIG. 11, distance
1138 at approximately the center of read sensor stack 1106 is
greater than distance 1136 at approximately the edge of read sensor
stack 1106.
[0082] Similar to read head 600 and read head 900, read head 1100
may be utilized in a magnetic read/write head to read data
contained on a magnetic storage medium in which the transition
boundaries between magnetic bit domains define a transition
curvature, such as, e.g., magnetic data track 250 of FIG. 2B. Read
head 1100 may fly over the surface of data track 250 to read the
data stored on magnetic storage medium by detecting the magnetic
fields of the respective magnetic bit domains aligned on data track
250. For example, magnetic read head 1100 may provide means for
creating a reader playback sensitivity function associated with the
magnetic read head 1100, the reader playback sensitivity function
substantially corresponding to a shape of the respective magnetic
bit domains aligned on the data tracks of a magnetic storage
medium. In some embodiments, the read playback sensitivity function
may be substantially similar to that represented by plot 500 of
FIG. 5.
[0083] Although the shape of cap layer 1115 of FIG. 9 is shown as
resulting in curved boundary 1135 that is a smooth, arcuate
boundary, it is recognized that configuration which do not possess
such a geometry may also allow for read head 900 to read data
contained on a magnetic storage medium in which the transition
boundaries between magnetic bit domains define a transition
curvature, e.g., by allowing for a read playback sensitivity
function similar to that of FIG. 5. In some embodiments, cap layer
1115 of read sensor stack 1106 may be configured in a manner such
that all or a portion of boundary 1135 is not arcuate but still may
effectively allow read head 1100 to adequately detect magnetic bit
domains and/or transitions exhibiting curved transition profiles,
e.g., according to a reader playback sensitivity function similar
that of FIG. 5. For example, the shape of cap layer 1115 proximate
to shield layer 1102 may be similar to one or more linear steps
along boundary 1135 such that distance 1138 at approximately the
center of read sensor stack 1106 is greater that distance 1136 at
approximately the edge of read sensor stack 1106, even though the
distance from the edge of the stack to approximately the center may
not be continuously increasing as shown in FIG. 11.
[0084] FIG. 12 is a transmission electron microscopy (TEM)
micrograph of an example read sensor 1200. Read sensor 1200
includes read sensor stack 1202 including cap layer 1204 similar to
that described with respect to FIG. 11. Read sensor also includes
insulator layers 1208A and 1208B proximate to sides of read sensor
stack 1202. Although shield layers, such as, e.g., shield layers
1102 and 1104 of FIG. 11, are not shown in example of FIG. 12, a
shield layer may be formed proximate to cap layer 1204 of read
sensor stack 1202 such that the boundary between the read sensor
stack 1202 and the shield layer proximate to cap layer 1204 may be
curved according to the shape of cap layer 1204. In such a
configuration, read sensor 1200 may be utilized in a read head the
same or similar as described with respect to read head 1100 of FIG.
11.
[0085] Furthermore, in the example of FIG. 12, the reader junction
of read sensor 1200 was formed using thin carbon as a hard mask
layer. Redeposition of material during the ion milling process to
form read sensor stack 1202 results in channels 1206A and 1206B
proximate to sides of read sensor stack 1202, and cap layer 1204 in
particular. As configured, channels 1206A and 1206B may provide
magnetic side-shield for read sensor 1200, e.g., when utilized to
sense magnetic fields as described herein.
[0086] Various embodiments of the disclosure have been described.
These and other embodiments are within the scope of the following
claims.
* * * * *